temperamental

1(usually disapproving)having a tendency to become angry, excited, or upset easily, and to behave in an unreasonable wayYou never know what to expect with her. She's so temperamental.(figurative)The printer's being temperamental this morning.He's a temperamental player (= he plays well or badly according to his mood).

2connected with someone's nature and personalityThey are firm friends in spite of temperamental differences.